The 13 bald eagles were found lifeless on a Maryland farm more than two years ago, many with wings splayed, bodies intact, and talons clenched. Several were too young to have their species’ distinctive white heads. And at least six, according to a federal lab report, had ingested a highly toxic pesticide that essentially has been banned from the U.S. market, in part because it is lethal to birds.

The report, obtained by the Annapolis radio station WNAV and shared with The Washington Post, answers one big question in a mysterious wildlife crime that angered conservation organizations and stumped U.S. Fish and Wildlife Service investigators, who were involved because the bald eagle is a federally protected species. Tests showed that the birds were poisoned, as officials suspected. What remains unsolved is who did it.